JP3297895B2 - Method for producing container lid made of synthetic resin having tamper-evident properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a synthetic resin container lid having a tamper-evident property (a characteristic in which traces of an improperly opened container remain on the container lid).

[0002]

2. Description of the Related Art As a well-known container lid applied to the mouth and neck of a glass or synthetic resin container for a soft drink or the like, a synthetic resin container lid having a tamper-evident characteristic is widely used. Have been. A typical example of such a synthetic resin container lid includes a container lid body formed of a suitable synthetic resin such as polypropylene or hard polyethylene. The container lid body has a top wall and a skirt wall hanging down from the periphery of the top wall, and a circumferential break line is formed on the skirt wall, and the skirt wall is a main part above the break line. It is partitioned into a tamper-evident hem below the break line. The circumferential breaking line is composed of a plurality of circumferentially spaced slits extending in the circumferential direction and a plurality of bridging portions remaining between the slits, and the tamper-evident foot has a plurality of hem portions. It is connected to the lower part of the skirt wall via a bridge.
A female thread is formed on the inner surface of the main part of the skirt wall. A locking flap piece protruding radially inward is formed on the inner surface of the tamper-evident skirt. Usually, an axial breaking line is formed at the tamper-evidence foot, and in this case, one (or several) of the plurality of bridging portions in the circumferential breaking line has a breaking strength of another bridge. The non-ruptured bridging part is larger than the bridging part. A liner, conveniently made of a relatively soft synthetic resin such as soft polyethylene or EVA (ethylene-vinyl acetate copolymer), is usually provided on the inner surface of the top wall.

[0003] The container lid as described above is applied to a container in which a male screw and an annular locking jaw located below the male screw are formed on the outer surface of a cylindrical mouth and neck. When sealing the mouth and neck of the container, the container lid is fitted over the mouth and neck of the container and rotated in the closing rotation direction, and the female screw thread formed on the inner surface of the main part of the skirt wall in the container lid body. Into the male thread formed on the outer surface of the mouth and neck. The locking flap piece formed on the inner surface of the tamper-evidence hem of the container lid body is elastically deformed, passed through the annular locking jaw formed on the outer surface of the mouth and neck, and then elastically deformed. And is locked to the lower surface of the annular locking jaw. When the container lid is attached to the mouth and neck as required, a liner disposed on the inner surface of the top wall of the container lid body is brought into close contact with the upper end of the mouth and neck, thereby sealing the mouth and neck. When opening the mouth and neck of the container, the container lid body is rotated in the direction opposite to the closing rotation direction, that is, in the opening rotation direction. Thus, since the female thread formed on the skirt wall of the container lid body is moved along the male thread formed on the mouth and neck, the container lid moves along the axis in the opening rotation direction. It is moved upward in the direction. However, since the locking flap piece formed on the inner surface of the tamper-evidence hem is locked to the annular locking jaw of the mouth and neck, the tamper-evidence hem moves upward in the axial direction. Along with the circumferential break line formed on the skirt wall, considerable stress is generated in the axial break line formed on the tamper-evidence hem, and the bridging portion in the circumferential break line is unbroken. At the same time, the rupture of the tamper-evident dent is made from an endless annular shape to a stripped shape. After a while, the tamper-evidence skirt is also allowed to freely rise upward in the axial direction,
The entire container lid is removed from the mouth and neck, and the mouth and neck are opened. If the tamper-evident hem does not have an axial break line, all bridging portions in the circumferential rupture line are broken, the tamper-evidence hem is separated from the main part of the skirt wall, and the tamper-evident hem is cut off. The other part of the container lid is removed from the mouth and neck, leaving the skirt of the evidence on the mouth and neck.

[0004]

In the container lid of the above-described embodiment, the container lid is detached from the mouth and neck part without breaking the normal bridging part (and the axial line) at the circumferential breaking line. It is important that the so-called container lid slip-through is reliably prevented from occurring. If the container lid slips through, it is possible to open the mouth and neck once, make unauthorized changes to the contents, then reattach the container lid to the mouth and neck and return to the original state, Properties are impaired. Furthermore, the container lid cannot be detached from the mouth and neck, but the container lid is rotated through an angle of, for example, 360 degrees, thereby separating the liner upward from the upper end of the mouth and neck and sealing the mouth and neck. Is canceled once,
Prior to this, it is also important that the bridging part in the circumferential breaking line is broken. If the bridging part in the circumferential breaking line is not broken even though the seal of the mouth and neck has been once broken, the contents may be corroded due to the break of the seal of the mouth and neck once. When the inconvenience occurs, there is a possibility that a situation may occur in which the inconvenience is not specified and the product is sold as a normal product.

However, in the conventional container lid of the above-described embodiment, the locking flap piece formed on the tamper-evident hem of the container lid body is moved to the annular locking jaw formed on the mouth and neck. Is not always sufficient, and the above-mentioned requirements cannot be sufficiently satisfied. For example, the locking flap piece passes through the locking jaw of the mouth and neck by being elastically bent with its base edge, that is, the connection edge with the inner surface of the tamper-evident hem as a bending edge,
Thus, the above-mentioned detachment of the container lid often occurred. To solve such a problem, Japanese Patent Application Laid-Open No. 4-31461 discloses that an inward curl is provided at the lower end of a tamper-evident hem of a container lid body. Such curls are formed as follows. In the container lid main body forming step, a thin projecting piece protruding downward from the lower end of the tamper evidence bottom is formed on the container lid main body. Thereafter, a curl forming step of causing the curl tool to act on the thin projecting piece by accommodating the thin projecting piece in a curl groove formed in the heated curl tool is performed.

According to the experiments conducted by the present inventors, according to the container lid provided with the curl, the locking action of the locking flap piece on the annular jaw of the mouth and neck portion is reinforced, and the conventional container lid has the same effect. Although it is possible to effectively prevent the container lid from slipping out as compared with the container lid, it is still not enough, and the probability is considerably small, but there is a risk that the container lid slippage will occur, and It has also been found that some rotation of the container lid has released the seal on the mouth and neck but has the potential to create a situation in which the bridging section cannot be broken at the circumferential break line. ing.

[0007] The present invention has been made in view of the above facts, and a technical problem of the present invention is to add a relatively simple additional step to the manufacture of a container lid including the container lid body of the above-described embodiment.
It is necessary to ensure that the container lid does not slip through, and that the bridging of the bridging line at the circumferential rupture line occurs sufficiently before the opening of the mouth and neck seal due to the rotation of the container lid. That is.

[0008]

As a result of diligent studies and experiments, the present inventors have developed a cylindrical restraining outer peripheral surface having a predetermined outer diameter after curl formation disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-31461. The restraining tool provided is inserted into the synthetic resin container lid body so that the cylindrical restraining outer peripheral surface is positioned radially inward of the curl, and the inner diameter is substantially the same as or larger than the outer diameter of the cylindrical restraining outer circumferential surface. It has been found that the above technical solution can be achieved by performing a curl crushing step in which a circular pressing surface of a heated crushing tool having a circular pressing surface and having the circular pressing surface act on the curl to crush the curl. .

That is, according to the present invention, as a manufacturing method for achieving the above technical object, there is provided a top wall and a skirt wall hanging down from a peripheral edge of the top wall, wherein the skirt wall comprises a main portion and the main portion. A tamper-evidence hem portion located below the tamper-evidence hem portion and a thin-walled protruding piece extending further downward from the lower end of the tamper-evidence hem portion, and protruding radially inward from the inner surface of the tamper-evidence hem portion A main body forming step of forming a synthetic resin container lid main body in which the locking flap pieces are disposed,
After the main body forming step, the thin protruding piece is housed in a curl groove formed in the heated curl tool, and the curl tool is caused to act on the thin protruding piece, whereby the thin protruding piece is curled inward. A method of manufacturing a synthetic resin container lid having a tamper-evident characteristic, comprising, after the curl forming step, a restraining tool having a cylindrical restraining outer peripheral surface having a predetermined outer diameter. An annular ring having an inner diameter substantially the same as or larger than the outer diameter of the cylindrical constrained outer peripheral surface while being inserted into the synthetic resin container lid body to position the cylindrical constrained outer peripheral surface radially inward of the curl. Providing a manufacturing method, comprising: a curl crushing step of crushing the curl by applying the annular pressing surface of a heated crushing tool to the curl having a pressing surface. It is.

[0010] A plurality of the locking flap pieces are formed on the inner surface of the tamper-evident foot at intervals in the circumferential direction, and each of the locking flap pieces is connected to the tamper-evident foot. The base edge is inclined in the opposite direction to the container lid closing rotation direction when the container lid is attached to the mouth and neck of the container, and is projected inward in the radial direction, and the base edge extends downward in the axial direction. In a case where the curl is extended in a direction opposite to the container lid closing rotation direction, the curl can be pressed against the lower edge of the locking flap piece in the curl crushing step. In the case where the base edge of the locking flap piece formed on the inner surface of the tamper-evident hem portion connected to the tamper-evidence hem portion extends substantially horizontally, the curl crushing step The curl can be pressed against the lower surface of the locking flap piece.

[0011]

In the synthetic resin container lid manufactured by the manufacturing method of the present invention, the curl is crushed in the curl crushing step, whereby the rigidity of the curl itself is increased and the crushed curl is engaged. It is pressed sufficiently tight against the lower edge or lower surface of the stopper flap piece. In this way, the function of preventing the curl against undesirable elastic deformation of the locking flap piece, such as the fact that the locking flap piece is elastically bent with its base edge as the bending edge, is sufficiently promoted, and thus the container lid can be sufficiently pulled out. This reliably prevents and also ensures that the bridging rupture at the circumferential breaking line occurs prior to the opening of the mouth and neck seal due to rotation of the container lid.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the manufacturing method according to the present invention will be described below in more detail with reference to the accompanying drawings.

FIG. 1 shows a preferred example of a synthetic resin container lid main body formed by a main body forming step. The container lid body indicated by reference numeral 2 includes a substantially circular top wall 4 and a substantially cylindrical skirt wall 6 hanging from the periphery of the top wall 4. The skirt wall 6 has a main portion 8, a tamper-evident hem portion 10 located below the main portion 8, and a thin projecting piece 12 extending further downward from the lower end of the tamper-evident hem portion 10. The outer surface of the main portion 8 of the skirt wall 6 is formed with an uneven shape 14 for preventing a finger locked thereon from slipping. Main part 8 of skirt wall 6
Is formed with a female thread 16 on the inner surface thereof. An axially extending ventilation notch 17 is formed in the female thread 16 at intervals in the circumferential direction. Tamper Evidence Hem 10
A plurality of locking flap pieces 18 are formed at intervals in the circumferential direction on the inner surface of the. Such locking flap piece 18
The direction from the base edge 20 connected to the inner surface of the tamper-evidence hem 10 to the closing rotation direction of the container lid 2 when the container lid 2 is mounted on the mouth and neck of the container as described later (FIG. 1).
At an angle in the opposite direction to the clockwise direction as viewed from above) and project inward in the radial direction. The base edge 20 of each of the locking flap pieces 18 also extends obliquely downward in the axial direction in a direction opposite to the container lid closing rotation direction. The thin protruding piece 12 extending downward from the lower end of the tamper-evident hem 10 has a cylindrical shape, the inner diameter of which is substantially the same as the inner diameter of the tamper-evidence hem 10, and the outer diameter of which is equal to the tamper-evidence hem. It is smaller than the outer diameter of the part 10.

The container lid main body 2 having the above-described configuration includes:
The synthetic resin, which is advantageously relatively rigid, such as polypropylene or rigid polyethylene, can be conveniently formed by known body forming processes, including compression molding or injection molding into the required shape. For details of the main body forming process itself, see, for example,
Since it is described in JP-A-51116, it is omitted in this specification.

Continuing with reference to FIG. 1, in the illustrated embodiment, a break line forming step is performed after the main body forming step, whereby the circumferential break line 22 is formed.
And an axial breaking line 24 is formed. The circumferential breaking line 22 that divides the skirt wall 6 into the main portion 8 and the tamper-evident hem portion 10 has a plurality of slits 26 extending in the circumferential direction at intervals in the circumferential direction and a plurality of slits 26 located between the slits 26. And two bridge portions 28.
One of the plurality of bridging portions 28 is a non-ruptured bridging portion 28A having a larger cross-sectional area than other bridging portions to increase strength. If desired, all bridging portions 28 can be broken bridging portions without providing the non-breaking bridging portions 28A. In this case, the provision of the axial breaking line 24 can be omitted. it can. Still referring to the formation of the circumferential break line 22, in the illustrated container lid body 2, the inner surface of the skirt wall 6 has a downwardly facing annular shoulder 3
0 is formed, and the inner diameter below the annular shoulder 30 is set somewhat larger than the inner diameter above it. Immediately below the annular shoulder 30, a plurality of ribs 32 are formed on the inner surface of the skirt wall 6 and extend in the axial direction at intervals in the circumferential direction.
The circumferential breaking line 22 is formed by cutting the skirt wall 6 in the circumferential direction while leaving the ribs 32. Such a cut made from the outer surface of the skirt wall 6 is not entirely cut in the circumferential direction, but is left partially without being cut in the circumferential direction. Therefore, the tamper-evident hem portion 10 below the circumferential breaking line 22 is separated from the circumferential cutting line 22 through the plurality of ribs 32 and the circumferential non-cutting portions that are left without being cut. Is also connected to the upper main part 8. A plurality of ribs 32 define a normal bridging portion 28, a cutting line between the plurality of ribs 32 defines a slit 26, and a circumferential non-cutting portion defines a non-ruptured bridging portion 28A. . Axial breaking line 2
Numeral 4 extends the tamper-evident foot portion 10 in the axial direction, and the upper end thereof is brought close to one end of the non-ruptured bridging portion 28A. Such an axial break line 24 can be conveniently constructed from a score generated from the inner or outer surface of the tamper-evident skirt 10 that is partially cut in the thickness direction rather than the entire thickness direction. The breaking line forming step for forming the circumferential breaking line 22 and the axial breaking line 24 may be performed before or after the curl forming step, the curl crushing step, and the liner forming step described below, if desired. It can also be performed in between. Further, in the illustrated embodiment, the cutting operation is performed in the breaking line forming step performed separately from the main body forming step to form the circumferential breaking line 22 and the axial breaking line 24, but if desired. For example, the slit in the circumferential breaking line and the score (or slit) in the axial breaking line can be formed at the time of compression molding or injection molding in the main body molding step.

FIG. 2 shows a curl forming step performed after the main body forming step and the break line forming step described above. In this curl forming step, the container lid main body 2 in the form shown in FIG. 1 is held in an inverted state (that is, a state in which the outer surface of the top wall 4 faces downward) by a suitable holding means (not shown). Is done. Then, the curl tool 34 is caused to act on the thin projecting piece 12 of the container lid body 2. An annular curl groove 36 is formed on the lower surface of the curl tool 34 of which only a part is shown. This curl groove 36
Has a semicircular shape in vertical section. At least the curl groove 36 of the curl tool 34 is heated to a required processing temperature (for example, about 110 to 120 degrees when the container lid body 2 is made of polypropylene). It is relatively lowered to the position shown in FIG. During the relative lowering of the curl tool 34, the thin protruding piece 12 extending in a cylindrical shape is gradually accommodated in the curl groove 36 from the protruding end thereof and deformed by heating. The surface is deformed into a curl 38 having a substantially circular shape.

In the present invention, it is important to perform a curl crushing step after the curl forming step.
Continuing the description with reference to FIGS. 3 and 4, in the curl crushing step, the container lid main body 2 in which the thin projecting piece 12 has been transformed into the curl 38 is turned upside down by a suitable holding means (not shown). And the container lid body 2
, A restraining tool 40 and a crushing tool 42 are applied. The restraining tool 40 has a cylindrical restraining outer peripheral surface 44, and the outer diameter of the restraining outer peripheral surface 44 is set to be substantially the same as or slightly smaller than the inner diameter of the curl 38 of the container lid body 2.
The crushing tool 42, which may have a cylindrical shape as a whole, is provided outside the restraining tool 40. On the lower surface of the crushing tool 42, a flat annular pressing surface 46 is formed. The inner diameter of the annular pressing surface 46 is set to be substantially the same as or slightly smaller than the outer diameter of the restraining outer peripheral surface 44 of the restraining tool 40. In the curl crushing step, first, the restraining tool 40 is lowered relative to the container lid body 2 to the position shown in FIG.
4 is positioned inside the curl 38. Next, at least the pressing surface 46 is at a required processing temperature (for example, 110 to 1 when the container lid body 2 is made of polypropylene).
Crushing tool 42 heated to about 20 degrees)
Is relatively to the container lid main body 2 and the restraining tool 40 in FIG.
Is lowered to the position shown in FIG. Crushing tool 4
During such a downward movement of 2, the heated pressing surface 46 is pressed against the curl 38, and the curl 38 is deformed by heating. The radial inward deformation of the curl 38 is limited by the restraining outer peripheral surface 44 of the restraining tool 40, so that the curl 38 is crushed and pressed against the lower edge of the locking flap piece 18 of the container lid body 2.

In the illustrated embodiment, a liner forming step is performed after the curl crushing step, and a liner 48 of a required form is provided on the inner surface of the top wall 4 of the container lid body 2 as shown by a two-dot chain line in FIG. Is formed. In a preferred example of such a liner molding step, a synthetic resin material in a softened and molten state is supplied to the inner surface of the top wall 4 of the container lid main body 2, and then a compression molding tool (not shown) enters the container lid main body 2. At the very least, it acts on the synthetic resin material to flow into a required shape, and thus the liner 48 is formed. Liner 4
As the synthetic resin for forming 8, a relatively soft synthetic resin such as soft polyethylene or EVA (ethylene-vinyl acetate copolymer) is conveniently used. If desired, a liner forming step can be performed prior to or during the breaking line forming step, curl forming step, and curl crushing step described above.

FIG. 5 shows a state in which a container lid 50 made of the container lid main body 2 and the liner 48 manufactured through the above-described various steps is mounted on the mouth and neck 52 of the container. . The mouth and neck portion 52 of the container, which can be formed of a suitable synthetic resin such as glass or polyethylene terephthalate, has a substantially cylindrical shape as a whole, and has an external thread 54 on its outer surface and an annular locking jaw located thereunder. A portion 56 is formed. After filling required contents such as soft drinks into the container, the container lid 50 is attached to the mouth and neck 52, and the mouth and neck 52 is sealed. When attaching the container lid 50 to the mouth and neck 52, the container lid 50 is fitted to the mouth and neck 52, and the container lid 50 is rotated in the closing rotation direction, that is, clockwise as viewed from above in FIG. Thus, the female screw thread 16 formed on the inner surface of the main part 8 of the skirt wall 6 of the container lid body 2 is replaced with the male screw thread 54 formed on the outer peripheral surface of the mouth and neck portion 52 of the container.
And screw them together. The locking flap piece 18 formed on the inner surface of the tamper-evident hem portion 10 of the skirt wall 6 of the container lid body 2 is elastically deformed upward to form the annular locking jaw portion 56 of the mouth-neck portion 52. After passing through, it is elastically restored and locked on the lower surface of the annular locking jaw 56. The liner 48 formed on the inner surface of the top wall 4 of the container lid body 2 is brought into close contact with the upper end surface of the mouth-neck portion 52, thereby sealing the mouth-neck portion 52.

When opening the mouth and neck 52 of the container, the container lid 50 is rotated in the opening rotation direction, that is, counterclockwise as viewed from above in FIG. As a result, the female thread 16 formed on the inner surface of the main portion 8 of the skirt wall 6 of the container lid body 2 is moved along the male thread 54 formed on the outer peripheral surface of the mouth-neck portion 52. The container lid 50 is raised with rotation. On the other hand, the tamper-evident hem portion 10 in the skirt wall 6 of the container lid body 2 is formed by an annular locking jaw portion 56 in which the locking flap piece 18 formed on the inner surface is formed on the outer peripheral surface of the mouth-neck portion 52. Is locked to the lower surface of the, so that upward movement is prevented. Thus, a considerable stress is generated in the bridging portion 28 in the circumferential breaking line 22 formed on the skirt wall 6 of the container lid body 2, and all the bridging portions 28 except the non-breaking bridging portion 28A are broken. You. Further, a considerable stress is also generated in the axial rupture line 24 formed in the tamper-evident foot portion 10, and the axial rupture line 24 is broken. Thus, the tamper-evident hem 10 is unfolded from the endless annular shape to an end strip, and the locking of the locking flap piece 18 to the annular locking jaw 56 of the mouth and neck portion 52 is released. The entire container lid 50 including the above can be raised. When the container lid 50 is raised to a certain extent, the liner 48 of the container lid 50 is separated from the upper end of the mouth-neck portion 52, and is formed between the upper end of the mouth-neck portion 52 and the liner 48 and in the female thread 16. The inside of the container is communicated with the outside through the ventilation notch 17 (FIG. 1). Thereafter, the entire container lid 50 is detached from the mouth and neck 52, and the mouth and neck 52 is completely opened.

Thus, in the container lid 50 manufactured by the manufacturing method of the present invention and in which the curl 38 of the container lid main body 2 is crushed, the container lid 50 is rotated in the opening rotation direction so that the mouth and neck 52 When opening the opening, the presence of the curl 38 which is crushed and pressed against the lower edge of the locking flap piece 18 causes the locking flap piece 18 to pivot downward about its base edge 20 so that the mouth and neck can be opened. It is reliably prevented from passing through the annular locking jaw 56 of the portion 52, and the container lid 50 can be moved from the mouth and neck 52 without breaking the bridging portion 28 and the axial breaking line 24 in the circumferential breaking line 22. Occurrence of the detached container lid is sufficiently and reliably prevented. Also, the locking flap pieces 18 are crushed and
Before the inside of the container is communicated with the outside, the presence of the curl 38 pressed against the lower edge of the container enhances the locking of the locking flap piece 18 to the annular locking jaw 56 of the mouth-neck portion 52. Bridge 28 at circumferential breaking line 22
The requirement that the axial breaking line 24 is broken can be satisfied relatively easily.

FIG. 6 shows a modified example of the container lid main body formed in the main body forming step. In the container lid body 102 shown in FIG. 6, a locking flap piece 118 extending continuously in the circumferential direction is formed on the inner surface of the tamper-evident skirt 110 in the skirt wall 106. The locking flap piece 118 is inclined upward from the base edge 120 connected to the tamper-evident foot 110 and protrudes inward in the radial direction. The base edge 120 of the locking flap 118 extends substantially horizontally. Notches 119 are formed in the locking flap pieces 118 themselves at intervals in the circumferential direction. Each of the notches 119 extends to the protruding edge of the locking flap piece 118, and the circumferential width thereof is gradually increased toward the protruding edge. If desired, instead of the circumferentially extending annular locking flap piece 118, a locking flap piece that is inclined upward from the substantially horizontally extending base edge and protrudes inward in the radial direction is circumferentially spaced. It is also possible to form a plurality. The configuration of the container lid body 102 shown in FIG. 6 other than the locking flap pieces 118 is substantially the same as the container lid body 2 shown in FIG.

The container lid body 102 shown in FIG. 6 is also identical to the container lid body 2 shown in FIG.
The fracture line forming process is performed by performing the fracture line forming process.
Then, an axial breaking line 124 is formed, and then a curl forming process is performed to heat-deform the thin cylindrical protruding piece 112 into a curl 138 (FIG. 7). Thereafter, a crushing step is performed. In the crushing step, as shown in FIG. 7, a restraining tool 40 having a cylindrical restraining outer peripheral surface 44 and a crushing tool 42 having an annular pressing surface 46 are provided.
(The restraining tool 40 and the crushing tool 44 may be exactly the same as the restraining tool 40 and the crushing tool 44 shown in FIGS. 3 and 4). Press In this crushing step, the restraining tool 40 is first moved relative to the container lid body 102 to the position shown in FIG. 3, just like the crushing step described with reference to FIGS. 3 and 4. As a result, the restraining outer peripheral surface 44 of the restraining tool 40 is positioned inside the curl 138. Next, at least the pressing surface 46 of the crushing tool 42 heated to the required processing temperature is lowered relative to the container lid body 102 and the restraining tool 40 to a position shown in FIG.

EXPERIMENTAL EXAMPLE Using a polypropylene having a density of 0.912 g / cubic cm and a melt flow rate at 230 ° C. of 10 g / 10 minutes, it was confirmed that neither a circumferential break line nor an axial break line was formed. Except for this, a container lid body having the form as shown in FIG. 1 was formed. Next, the curl forming step described with reference to FIG. 2 is performed to transform the thin projecting piece of the container lid body into a curl, and then the crushing step described with reference to FIGS. 3 and 4. 5 to crush the curl, and further press-mold a liner on the inner surface of the top wall of the container lid body, except that no circumferential and axial break lines are formed.
A container lid as shown in FIG. The total height of the container lid was 20.0 mm, and the valley diameter formed on the inner surface of the main part of the skirt wall was 27.7 mm. The axially projecting length of the thin projecting piece before being deformed into a curl is 3.0 m.
m and its thickness was 0.4 mm. Made of polyethylene terephthalate, which is commercially available as a container for cola and has an inner volume of 1500 ml and a male thread formed on the outer peripheral surface of the mouth and neck portion as shown in FIG. In a bottle, put a commercially available cola at approximately 0 ° C.
After cooling and filling, and washing the outer peripheral surface of the mouth and neck with tap water, a container lid was attached to the mouth and neck. When mounting the container lid, a torque of 15 kg · f · cm was applied to the container lid. After leaving the bottle equipped with the container lid at room temperature for 24 hours, the so-called slip-through torque required for forcibly rotating the container lid in the opening direction and detaching the container lid from the mouth and neck was measured. 1
Table 1 shows the results of measuring the slip-through torque of the zero container lid.

COMPARATIVE EXPERIMENTAL EXAMPLE For comparison, the same procedure as in the above experimental example was repeated except that the curl crushing step was not performed, and thus the curl of the container lid was not crushed. Table 1 below shows the results of measuring the slip-through torque of the container lid.
It was as follows.

[0026]

[Table 1]

[0027]

In the container lid manufactured by the manufacturing method of the present invention, the locking action of the locking flap piece on the annular locking jaw of the mouth and neck of the container is enhanced, and the breaking line is broken as required. The container lid is effectively prevented from slipping out of the container's mouth and neck without being removed, and also before the container's mouth and neck is unsealed when the container lid is rotated in the opening rotation direction. In this case, the breaking line can be broken.

[Brief description of the drawings]

FIG. 1 is a side view, partially in section, of a container lid main body formed by performing a main body forming step and a break line forming step in a preferred embodiment of the manufacturing method of the present invention.

FIG. 2 is a partially enlarged view showing a curl forming step performed on the container lid main body shown in FIG.

3 is a partially enlarged cross-sectional view showing the first half of a curl crushing step performed on the container lid body shown in FIG.

FIG. 4 is a partially enlarged cross-sectional view showing the latter half of the curl crushing step performed on the container lid main body shown in FIG.

FIG. 5 is a side view, partially in section, showing a state in which the container lid manufactured by the preferred embodiment of the manufacturing method of the present invention is attached to the mouth and neck of the container.

FIG. 6 is a side view, partially in section, of a modified example of the container lid main body formed by the container lid main body forming step and the retraction of the breaking line in the manufacturing method according to the present invention.

FIG. 7 is a partially enlarged cross-sectional view showing the latter half of the curl crushing step performed on the container lid main body shown in FIG. 7;

[Explanation of symbols]

 2: container lid body 4: top wall 6: skirt wall 8: main part of skirt wall 10: tamper evidence hem 12: thin protruding piece 16: female thread 18: locking flap piece 20: locking flap piece Base 22: Circumferential breaking line 24: Axial breaking line 34: Curl tool 36: Curl groove 38: Curl 40: Restraint tool 42: Crush tool 44: Constraint outer peripheral surface of restraint tool 46: Annular pressing of crush tool Surface 48: liner 50: container lid 52: mouth and neck 54: male thread 56: annular locking jaw 102: container lid body 106: skirt wall 110: tamper-evident hem 118: locking flap piece 120: engagement Base edge of stop flap piece 122: circumferential breaking line 124: axial breaking line 138: curl

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-311461 (JP, A) JP-A-6-99999 (JP, A) JP-A-5-509277 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B65D 41/34

Claims (3)

(57) [Claims] 1. A top wall and a skirt wall hanging from a periphery of the top wall, wherein the skirt wall has a main part, a tamper-evident hem located below the main part, and the tamper-evident hem. A thin projecting piece extending further downward from the lower end of the synthetic resin container lid body, wherein a locking flap piece protruding inward in the radial direction is provided on the inner surface of the tamper-evident hem. The main body forming step of molding and after the main body forming step, the thin protruding piece is housed in a curl groove formed in a heated curl tool, and the curl tool is caused to act on the thin protruding piece. A curl forming step of deforming the thin protruding piece into an inward curl, a method of manufacturing a synthetic resin container lid having a tamper-evident characteristic. A restraining tool having a surface is inserted into the synthetic resin container lid body to position the cylindrical restraining outer peripheral surface radially inward of the curl, and has substantially the same outer diameter as the cylindrical restraining outer circumferential surface. And a curl crushing step of crushing the curl by applying an annular pressing surface of a heated crushing tool to the curl having an annular pressing surface having a larger inner diameter. . 2. The tamper-evident skirt has a plurality of locking flaps disposed on the inner surface of the tamper-evident skirt at intervals in a circumferential direction, each of the locking flaps being tamper-evident hem. The base edge is inclined in the opposite direction to the container cover closing rotation direction when the container cover is attached to the mouth and neck of the container from the base edge connected to the container, and is projected inward in the radial direction. The container according to claim 1, wherein the curl is pressed downward against the lower edge of the locking flap piece in the curl crushing step. Production method. 3. The locking flap piece formed on the inner surface of the tamper-evident hem portion, the base edge of the locking flap piece connected to the tamper-evident hem portion extends substantially horizontally, and the curl crushing is performed. The method according to claim 1, wherein the curl is pressed against a lower surface of the locking flap piece in a step.